1. Field of the Invention
The present invention concerns an automatic bypassing device for tying posts or of stakes in fruit-bearing hedges. It also deals with agricultural machines equipped with such a device.
More precisely, the invention concerns an automatic bypassing device for tying posts for agricultural machines featuring a working head shaped for straddling a fruit-bearing hedge growing on staking posts or on tying wires, such as a row of vine stock, this tying including at least one or generally several superposed and spaced wires being supported from place to place by posts made of a rigid and solid material such as wood, metal (galvanized wire, steel, aluminum-zinc alloy, etc.), concrete, composite materials, etc.
It applies more specifically to machines for the cutting and trimming of fruit-bearing hedges.
The description below deals therefore more specifically with this very interesting application of the device of the invention to machines fitted and used for trimming vine stock, but it is emphasized that the reference to a trimming machine in the course of this disclosure does not have any limiting character whatsoever.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
As is generally known, the purpose of mechanical trimming of the vine stock is to simplify the ulterior work of the cutter by eliminating as much wood as possible prior to the manual cutting work.
During this preparatory operation, the wooden parts or canes, the tendrils of which are attached to the tying wires, are cut into pieces and removed. The great difficulty of this work lies in ensuring the bypass of the posts which constitute obstacles to the forward movement of the cutting parts of the working head of the machine, the constraint being that the action of the latter must not be destructive with respect to the posts and the tying wires, or to its own cutting elements.
The majority of currently used trimming machines utilize rotating cutting systems.
The working head of these machines comprises two stacks of rotating cutting parts that are spaced and mounted on vertical drive shafts. These stacks which are offset in the vertical direction are able to occupy two positions, namely: a working position with the tools brought closer together, where the edges of the rotating cutting elements of the two stacks intersect; and an opened position permitting the bypassing of the tying stakes, where the stacks of rotating tools find themselves separated by a vertical space.
Several devices have been proposed for the automatic opening of the working head as they pass the posts.
According to document EP-0 147344, this automatic opening is obtained by the shaping of the cutting tools stacked around the vertical drive shafts. These cutting tools comprise a rotating circular cage which is provided, on its periphery, with notches that are separated by teeth and in this cage are housed fixed cutting blades, said cage and said blades being fitted in a complementary fashion and linked together, to constitute a system of blade and counter-blade producing a shearing cut.
The turning cages of the cutting tool stacks are driven in rotation at a tangential speed that is essentially equal to the linear forward speed of the carrier vehicle on which the working tool of the machine is mounted, so that when the stacks of tools in the closer position encounter a tying post, the latter does not sustain any shock because of the fact that said stacks roll over the post without damaging it and without any risk of deterioration of the cutting tools.
The other particularly advantageous results obtained because of the trimming machine described in document EP-0 147 344 are shown in said document. However, this machine which has been enjoying a great success is relatively expensive.
That is why it has been offered to reduce this cost by replacing one of the stacks of cutting tools of the working head with a stack of feeder disks (see for example FR-2 635 252), but the results obtained by such a hybrid arrangement are clearly less satisfying.
So there are trimmers available on the market that feature a working head or cutting head consisting of more rustic cutting tools whereby it is possible to offer them for sale at more attractive prices, meeting the wishes of certain users. The cutting system of these machines comprises two stacks of fracturing elements constituted by steel disks that are notched on their periphery so as to form alternating teeth and recesses.
To improve the quality of wood cuts, the peripheral teeth of the cutting disks can be sharpened. The cutting tools or disks thus produced can be stacked on two vertical shafts at a regular distance from each other in the order of a few centimeters, 10 cm for instance.
The two vertical shafts are positioned on each side of the tying wires and are set so that the right and the left stacking disks intersect each other a few centimeters, 5 cm for instance, apart in the horizontal plane, in the closer working position, and are positioned a few millimeters from each other, 10 mm for instance in the vertical plane.
The crossing of the right stacking disks with the left stacking disks ensure the cutting off and the fragmenting of the wood of the fruit-bearing hedge.
The speed on the periphery of the rotating cutting disks must be twice the moving speed of the machine, so as to facilitate the cutting of the wood and to obtain a good cleaning of the tying wires.
This rotation speed of the disks can be adjusted by means of a flow divider that the hydraulic rotational drive system of said cutting disks is equipped with.
As the two stacks of toothed cutting disks are being kept under pressure against the fruit-bearing hedge, and in order not to be distanced from each other under the cutting force of the vegetation, they must be spread apart by the operator at the passage of each tying post. As the disks rotate at a peripheral speed above the forward speed of the machine, if the operator does not move the stacks apart, the tying posts could be damaged if they are made of wood, or cause the deterioration of the disks when said posts are made of steel or concrete. Likewise, at the entrance and exit of the row of vine stock forming the fruit hedge, the stacks of cutting disks are spread apart in order not to cut the abutment wires.
The tying wires must be properly tensioned so they won't be caught or cut off during the movement of the machine in the row.
Most of the current systems of the type described are unable to provide an automatic opening of the cutting head when passing the posts.
Certain manufacturers propose solving this problem by using opening wheels which are mounted in lieu of one of the disks of each stack, one on the drive shaft of the right stack and one on the drive shaft of the left stack.
These opening wheels have a diameter slightly larger than the diameter of the toothed cutting disks, for instance a diameter that is 2 cm larger than the diameter of the cutting disks, so that when the cutting stacks pass the tying posts, the latter will be in contact only with the opening wheels and not with the cutting disks.
These wheels are, in certain cases, driven in rotation directly by the same drive shaft as the stacks of cutting disks (see for example US 2006/0162309).
Since the peripheral speed of the opening wheels is above the forward speed of the machine so as to avoid unsatisfactory cutting of the woods, the main disadvantage of such a system is that the posts are being pulled backwards and possibly twisted or broken when the wheels come into contact with the posts.
In certain cases, the opening wheels are mounted through the intermediary of a bearing, so that they run idle. In this case, since these opening wheels are not driven in rotation, the main disadvantage of such an arrangement is that the tying posts are being pushed forward, and possibly become twisted or broken when the wheels come in contact with said posts.
Another known possibility is to mount the opening wheels through the intermediary of a bearing on the drive shafts and to drive them in rotation by a driving element that is exterior to the stacks, for example by a transmission belt or chain type. The major disadvantages of such a system are its complexity, its space requirements and the relatively high cost.
One aim of the present invention is to remedy the aforementioned disadvantages of the trimming machines of the kind featuring a working head comprising two vertical drive shafts on which are mounted two stacks of toothed cutting disks and an opening wheel.